1. Field of the Invention
This invention relates to a process for the production of a substantially tar-free "ENE" reaction product of an ethylenically unsaturated alpha, beta dicarboxylic acid compound and an ethylenically unsaturated long chain compound having at least 10 carbon atoms. More particularly this invention relates to a process using an alkyl aluminum halide, such as ethylaluminum dichloride (EtAlCl.sub.2), as a catalyst during the "ENE" reaction of an ethylenically unsaturated long chain compound having at least 10 carbon atoms and an ethylenically-unsaturated alpha, beta dicarboxylic acid compound.
2. Setting of the Invention
The "ENE" reaction products can be used for a variety of purposes such as in adhesives, insulating oils, as a raw material in the production of synthetic lubricating oils, preservatives, polyesters, additives in lubricants and fuels, etc. A very important use of these products is as a raw material for the manufacture of additives to improve the characteristics of fuels and lubricants. Most commonly, the reaction product of a substituted dicarboxylic acid compound, and an amine compound, such as a polyamine, can be used in gasolines and lubricants. These additives are often useful in fuels such as gasolines to inhibit rust, carburetor deposits, carburetor icing, etc., and as dispersants in motor oils to prevent the formation of harmful deposits on engine surfaces caused by oxidation products of lubricants and fuels, wear products, ingested dirt, etc.
The "ENE" reaction between an ethylenically unsaturated long chain compound having at least 10 carbon atoms and an alpha, beta unsaturated dicarboxylic acid compound involves the addition of the unsaturated long chain compound having at least 10 carbon atoms to one of the vinyl carbons of the unsaturated dicarboxylic acid compound. An example of the reaction is the addition of polyisobutylene to maleic anhydride: ##STR1##
The uncatalyzed "ENE" reaction between an ethylenically unsaturated long chain compound having at least 10 carbon atoms and an ethylenically unsaturated alpha, beta dicarboxylic acid compound has a major drawback. The unsaturated dicarboxylic acid compound suffers decomposition at elevated temperatures causing the formation of tar and other resinous byproducts. Thermal decomposition of ethylenically unsaturated alpha, beta dicarboxylic acid compounds at temperatures in excess of 100.degree. C. has been known and reported, for example, in U.S. Pat. No. 3,476,774. Such thermal decomposition can be accompanied by the evolution of water vapor and oxides of carbon. Under some observed conditions, the thermal decomposition can be explosive. In the absence of explosive decomposition, the thermal decomposition of the reactants and reaction products form carbon containing residues which are manifest in granular and tarry forms. Since the granular residue tends to remain suspended in the reaction product and cannot be removed easily therefrom, the desired product has a poor color rating and is often commercially unacceptable. The resinous tar-like residue tends to coat the internal surface of the reaction vessel, thereby necessitating the periodic shutdown and cleaning of the tarry material from the reactors. Obviously, the destruction of the ethylenically unsaturated alpha, beta dicarboxylic acid compound by thermal decomposition is also economically undesirable.
A variety of tar and resinous byproduct inhibitors for the "ENE" reaction have been proposed by the prior art. In general there are at least four types of inhibitors: (1) substituted benzene sulfonic acids, (2) halogenated compounds such as halogenated polymers or dibromohydantoin, (3) phenothiazine and quinone-type compounds and (4) boron compounds. These inhibitors have met with various degrees of success in reducing the formation of tars.
The tar is substantially a thermal decomposition product of the unsaturated dicarboxylic acid compound and the "ENE" reaction which is normally run at temperatures of between 100.degree. C. to 300.degree. C., preferably from about 200.degree. to 250.degree. C. It appears that it is the high temperature reaction environment which causes the formation of the tar and other resinous material. Therefor, there exists a need for a process which can reduce the temperature requirements of the "ENE" reaction of ethylenically unsaturated alpha, beta dicarboxylic acid compounds and an ethylenically unsaturated long chain compound having at least 10 carbon atoms, thereby reducing the energy requirements for the reaction and further reducing the formation of tar and other resinous byproducts.
The use of an alkyl aluminum halide as a Lewis acid catalyst to reduce the temperature requirements in the reaction of methyl propiolate with unactivated alkenes is disclosed in Snider, J. et al., Lewis Acid Catalyzed Reactions of Methyl Priopiolate with Unactivated Alkenes, Journal American Chemical Society 101, 5283 (1979). However, nowhere is it disclosed within Snider to use the alkyl aluminum halide to reduce the temperature requirements of and prevent the formation of tar in the reaction of ethylenically unsaturated alpha, beta dicarboxylic acid compound and an ethylenically unsaturated long chain compound having at least 10 carbon atoms. The use of other catalysts in the "ENE" reaction is disclosed in Hoffmann, H., The Ene Reaction, Agnew. Chem. Intl. Ed. Vol. 8, p. 556 (1969). However nowhere is it disclosed in Hoffmann to use an alkyl aluminum halide as a catalyst in the reaction of ethylenically unsaturated alpha, beta dicarboxylic acid compound and an ethylenically unsaturated long chain compound having at least 10 carbon atoms.